The present invention relates generally to switch assemblies and more particularly to a switch assembly especially suitable for use as part of a high voltage circuit breaker.
Circuit breakers generally are well-known in the art. In those situations where they are intended for use in high and ultra-high voltage circuits, for example on the order of 15,000 volts, it is essential that the breaker itself be trip-free in any position. That is, whether the breaker is closed or moving to its closed position, it is essential that an operator be able to override the closing mechanism at any time and cause the breaker to open immediately. In order to meet this objective, one typical type of high voltage circuit breaker utilizes a series of interconnected links which, in turn, are connected to breaker contacts for opening and closing the latter as the links move between a first, open positional configuration and a second, closed configuration.
While it has been found to be highly desirable to design high voltage circuit breakers utilizing an arrangement of links, because of the override requirements discussed above, the typical link arrangements have been relatively complicated, requiring at least four links in order to provide override capabilities. An example of this is illustrated schematically in FIGS. 1A, 1B and 1C. The overall circuit breaker shown there is generally indicated by the reference numeral 10 and includes a fixed contact 12 and a movable contact 14, both of which are adapted for connection into a high voltage circuit for opening and closing the latter. Circuit breaker 10 also includes a switch assembly 16 which will be described in more detail immediately below. For the moment it suffices to say that assembly 16 is connected to movable contact 14 through suitable means such as a connecting bar 18 in order to move contact 14 between its opened, solid line position spaced from contact 12 and its closed, dotted line position directly against contact 12.
Referring specifically to FIG. 1A, switch assembly 16 is shown including a four-link arrangement consisting of links 20, 22, 24 and 26. Link 20 is itself mounted for pivotal movement by suitable pivot means 27 and is also pivotally connected at one end to connecting bar 18 and at its other end to one end of link 22. The opposite end of link 22 is pivotally connected to one end of link 24 which has its opposite end pivotally connected to link 26. The four links are shown in FIG. 1A in a positional configuration in which the contact 14 is just beginning to move from its opened position downward to its closed position. Note that the free end of link 26 rests against the movable latch or stop 28. Link 26 is biased in this position by suitable means such as spring 29 which applies force F1 onto the link, as shown. In actuality, the spring is intended only to diagrammatically represent a suitable means for providing that biasing force onto the link so that the latter remains in the position illustrated so long as the latch remains in the position shown. At the same time, a cam member 30 or any other suitable means is provided for applying an upward force F2 against the bottom end of link 22, as shown in FIG. 1. In the case of cam member 30, the upward force F2 can be provided by rotating the cam member clockwise, as indicated by arrow 32.
Still referring to FIG. 1A, the application of force F2 onto the underside of link 22 in the manner shown causes the link to move upward, as indicated by arrow 34. This, in turn, causes the left end of link 24 to pivot upward, as indicated by arrow 36 and the left end of link 20 to pivot downward about pivot point 27, as indicated by arrow 38. This latter movement, in turn, causes the interconnecting link 18 to move downward, as indicated by arrow 40, thereby causing contact 14 to move into engagement with contact 12.
It is important to note that during the various movements of links 20, 22 and 24 described immediately above, link 26 remained stationary, biased against latch 28 by biasing force F1. In the case of circuit breaker 10, so long as link 26 remains in that position, cam member 30 can be rotated between extreme positions in order to apply and remove force F2 in order to cause the arrangement of links 20, 22 and 24 to move between the positional configuration illustrated in FIG. 1A for opening contacts 12 and 14 and the positional configuration shown in FIG. 1B for closing the contacts.
Referring specifically to FIG. 1B in conjunction with 1C, it will now be shown how link 26, the fourth link in the overall arrangement of links, is used as an override to cause the contacts 12 and 14 to open immediately regardless of the positional configuration of the other three links. As indicated above, link 26 is normally biased against latch 28. By rotating the latch clockwise or counterclockwise it is taken out of the path of movement of link 26, thereby allowing force F1 (see FIG. 1A) to immediately cause the link to pivot about a support point 41, as indicated by arrow 42. This causes the left-hand end of the link, as viewed in FIG. 1B, to pivot upward and to the right as indicated by arrow 44 and its right end to pivot downward and to the left as indicated by arrow 46. This in turn causes the joining point between links 22 and 24 to pivot upward and to the left, as indicated by arrow 48 while the joining point between links 20 and 22 pivot downward, as indicated by the arrow 50. These various movements ultimately cause the left-hand end of link 20 to pivot upward and to the right, as indicated by arrow 52, thereby pulling contact 14 forward and away from contact 12, as illustrated in FIG. 1C. It is important to note from FIG. 1C that these various movements cause the link 22 and all other links making up the overall arrangement to move away from force-applying cam member 30 so that the latter has no further effect on the arrangement. In other words, it is not necessary to take positive steps in removing the force F2 in order to "trip" the system and override the force in order to immediately open the contacts. It merely requires moving the link 26 in the manner illustrated.
The foregoing has been a description of a prior art type of circuit breaker utilizing four links to provide immediate override capabilities in order to open the breakers at any time during its operation. It is to be understood that only those components of the overall circuit breaker pertinent to the present discussion have been illustrated. Other components including, for example, the various support structure, have been omitted for purposes of clarity. While this particular design appears to function in a satisfactory manner to provide the desired override capabilities, it does require four links which makes a relatively complicated device from a structural standpoint. Nevertheless, applicant is not aware of any heretofore available link-type circuit breakers which do not utilize at least four links in order to provide desired override capabilities.